#include<stdio.h>
int main(){
	double r1 = 0.0;
	double r2 = 0.0;
	scanf("%lf%lf",&r1,&r2);
 	double s = 3.14*(r1*r1 - r2*r2);
	printf("%.2lf\n",s);
	return 0;
} 
